Ribonuclease (RNase) is the name of a group of enzymes that change ribonucleic acid (RNA) by digesting (cutting) phosphorus-oxygen bonds. The RNases are the subject of wide investigation in the laboratory, though scientists are still learning the many ways they work in living cells.

The best-studied RNase is from the pancreas of cattle. Its main portion, called ribonuclease A, was the first enzyme whose entire sequence of amino acids was determined. It was also the first protein to be totally synthesized from amino acid.

Pancreatic ribonuclease was first described in 1920 by the American biochemist Walter Jones (1865-1935), who showed that it could digest yeast RNA. It was partially purified in 1938 by the American microbiologist René Jules Dubos (1901-1982) and isolated in crystalline form late two years later by M. Kunitz. RNase's sequence and three-dimensional structure were determined in 1962 by the American biochemists Christian Anfinsen (1916-1995), Stanford Moore...